The invention relates to titanium inspection methods and systems. In particular, the invention relates to methods and systems for inspecting titanium using ultrasonic energy.
Nondestructive evaluation by ultrasonic inspection and ultrasonic inspection testing is a known material testing and evaluation method. Ultrasonic testing typically requires that detectable flaws possess different acoustic behaviors from bulk material under similar ultrasonic inspection. This different behavior permits the ultrasonic inspection technique to detect flaws, grains, imperfections, and other related microstructural characteristics for a material.
Materials with large, elastically anisotropic grains, such as, but not limited to, cast ingots of steels, titanium alloys, and nickel alloys, are often difficult to evaluate by ultrasonic testing. The difficulties arise, at least in part to, because sound waves, which are used for ultrasonic inspection, can be partially reflected from grains, and represent a background xe2x80x9cnoise.xe2x80x9d The generated background noise can mask flaws in the material, and is thus undesirable.
Ultrasonic inspection techniques have been developed that use focused ultrasonic beams to enhance a flaw fraction within any instantaneously insonified volume of material. These developed ultrasonic inspection techniques can identify indications based both on maximum signal, as well as signal to noise. A scattering of sound in a polycrystalline metallic material body, which is also known in the art as an attenuation of a propagating sound wave, can be described as a function of at least one of the following: grain dimensions, intrinsic material characteristics, and ultrasound frequency. Typically, three different functional relationships among scattering, frequency, and grain dimensions have been described. These are:
for xcex greater than 2xcfx80D, a=Tv4"THgr", termed xe2x80x9cRayleighxe2x80x9d scattering;
for xcex less than 2xcfx80D or xcexxe2x89xa1D, a=Dv2xcexa3, termed xe2x80x9cstochasticxe2x80x9d or xe2x80x9cphasexe2x80x9d scattering; and
for xcex less than  less than D, axe2x88x9d1/D, termed xe2x80x9cdiffusionxe2x80x9d scattering;
where a is attenuation, xcex is wavelength of the ultrasound energy, v is frequency of the ultrasound energy, D is an average grain diameter, T is a scattering volume of grains, and "THgr" and xcexa3 are scattering factors based on elastic properties of the material being inspected.
The microstructure of a material can determine the applications in which the material can be used, and the microstructure of a material can limit the applications in which the material can be used. The microstructure can be determined by measuring the scattering of sound waves in a material. The scattering of sound in a material, such as titanium, is sensitive to its microstructure. The titanium microstructure""s sound scattering sensitivity can be attributed to xcex1Ti particles that are arranged into xe2x80x9ccolonies.xe2x80x9d These colonies typically have a common crystallographic (and elastic) orientation, and these colonies of xcex1Ti particles can behave as large grains in the titanium material. An individual xcex1Ti particle might be about 5 xcexcm in diameter, however, a colony of xcex1Ti particles could be greater than about 200 xcexcm in diameter. Thus, the size contribution attributed to sound scattering sensitivity from xcex1Ti particles could vary over 40-fold among differing microstructures. Additionally, the sound scattering sensitivity due to xcex1Ti particles could change between that from randomly oriented xcex1Ti particles to that from xcex1Ti particles within oriented colonies of xcex1Ti particles.
Colony structures are formed during cooling a titanium alloy from a high temperature as xcex2Ti transforms to xcex1Ti . There is a crystallographic relation between the xcex1Ti and the parent xcex2Ti grain, such that there are only three crystallographic orientations that xcex1Ti will take when forming from a given xcex2Ti grain. If the cooling rate is high and there is uniform nucleation of xcex1Ti throughout the grain, neighboring xcex1Ti particles have different crystallographic orientations, and each behave as distinct acoustic scattering entities. However, if there are only a few sites of xcex1Ti nucleation within the xcex2Ti grain, then the xcex1Ti particles in a given area all grow with the same crystallographic orientation, and a colony structure results. This colony becomes the acoustic entity. Since a colony is formed within a xcex2Ti grain, the colony size will be less than the xcex2Ti grain size. The size of xcex2Ti grains and the nature of xcex1Ti particles colony structures are important variables that influence ultrasonic noise and ultrasonic inspection in single phase and two-phase titanium alloys and materials. Therefore, the size of xcex2Ti grains and the nature of xcex1Ti particles in colony structures may influence ultrasonic inspection techniques, methods, and results by creating undesirable noise during ultrasonic inspection. While thermomechanical processing techniques, which rely on dynamic recrystallization in the xcex1+xcex2 temperature range to achieve uniform fine grain (UFG) xcex1Ti particles and prevent colony formation, have been developed to improve titanium microstructure, defects may remain in the titanium material. These defects may be undesirable for some titanium material applications.
Thus, in order to have acceptable titanium for certain applications, it is desirable to provide an ultrasonic inspection process that accurately determines the nature of noise during ultrasonic inspection. The ultrasonic inspection method should determine if ultrasonic noise is attributed to a defect in the titanium material, or is due to other factors.
Therefore, a need exists for an ultrasonic inspection method for determining material characteristics and properties. Further, a need exists for an ultrasonic inspection method for determining processed titanium characteristics and properties. Furthermore, a need exists determining material configurations and characteristics for accurate ultrasonic inspection methods.
In one aspect of the invention, an ultrasonic inspection method for determining acceptability of material for microstructurally sensitive applications is provided. The method comprises providing a material, directing ultrasonic energy of ultrasonic inspection to the material; scattering reflected energy in the material; determining an amount of noise generated by the ultrasonic inspection; and characterizing the material as acceptable if the amount of noise corresponds to a preset noise level.
In another aspect of the invention, a system for implementing the method, as embodied by the invention is provided. The ultrasonic inspection system for determining acceptability of material for microstructurally sensitive applications comprises means for providing a material, means for directing ultrasonic energy of ultrasonic inspection to the material; means for scattering reflected energy in the material; means for determining an amount of noise generated by the ultrasonic inspection; and means for characterizing the material as acceptable if the amount of noise corresponds to a preset noise level.
These and other aspects, advantages and salient features of the invention will become apparent from the following detailed description, which, when taken in conjunction with the annexed drawings, where like parts are designated by like reference characters throughout the drawings, disclose embodiments of the invention.